1. Technical Field
The present invention relates to a projector.
2. Related Art
Currently, a projector having a liquid crystal panel includes heat-conductive and light-transmissive substrates affixed to both surfaces (light incident surface and light exit surface) of a polarization plate is known (for example, see JP-A-2004-198596). The heat-conductive and light-transmissive substrates are constituted by sapphire or crystal.
According to the related-art projector having the heat-conductive and light-transmissive substrates attached to both surfaces of the polarization plate, heat generated from the polarization plate (such as heat generated by absorption of light) is released to the outside of the system via the light-transmissive substrates. Thus, temperature increase of the polarization plate can be prevented.
In recent years, there is a demand for increase in quality of projection images by such methods as increasing contrast of the images projected from the projector and reducing unevenness of contrast and color.
According to the related-art projector, however, in the case of the light-transmissive substrate made of sapphire, crystal, quartz, heat-resisting glass, or white plate glass, heat distribution is generated in the plane by heat conducted from the polarization plate. In this case, difference in expansion amount is produced due to temperature difference at the respective positions. As a result, stress is generated inside the light-transmissive substrates. Then, phase retardation (phase retardation caused by heat distortion) of light passing through the light-transmissive substrates is produced. When the phase retardation increases by heat distortion, irregularity of polarization of light passing through the light-transmissive substrates also increases. Thus, contrast of the projection image is lowered, or unevenness of contrast and color is produced according to the in-plane distribution. As a result, the quality of the projection image becomes lower.